In the 37" 2x4 you will need to cut a 1'
3" long slot which is 3/8" wide. This is the slot that
the carriage bolt will slide through when you adjust the angle.
I cut this slot using a jigsaw (also called a scroll saw). First,
mark the beginning and end of the slot. Using a 3/8" drill
bit, drill a hole at the beginning and end of the slot. This will
give you a starting and ending point from which to insert the jigsaw
blade. Draw an outline of the slot between each hole so you have
a guide and saw out the slot. I found this a bit tough (hadn't used
a jigsaw before), but as long as you don't go way outside the lines,
you can always fix it up. Once you've drilled out the slot, take
a 3/8" bolt and slide it through the length of it to make sure
you have sufficient width along the entire length. (Those with routers
already know how easy this will be for them).
Steve Baird from Australia sent in the great suggestion
of clamping down another board to act as a guide for the jigsaw
to ride against. He says "simply measure the distance between
the blade and the edge of the base on the saw to calculate the position
to clamp the guide. Don't forget to allow for the width of the saw
blade. If the rear support is not wide enough then clamp another
piece of timber next
to it to support your guide."
Attach another hinge to
the bottom of this piece, in the same manner you did to the
top piece. Leave the assembly until we've completed a few more steps.
Proceed to the next step: shelf...